Rodless power cylinders utilize fluid pressure to move a piston reciprocally within a longitudinal bore of a cylinder. A longitudinal slot extends along the length of the bore and from the bore through the upper portion of the cylinder. It is important that the slot in the cylinder be sealed during movement of the piston to prevent fluid leakage and to maintain the proper fluid pressures within the cylinder. The movement of the piston within the cylinder is transferred exteriorly of the cylinder by a bracket assembly which is connected at one end to the cylinder and extends through the longitudinal slot in the cylinder. The other end of the bracket is mechanically connected to a trolley assembly which slidably engages the exterior of the cylinder. The trolley assembly stabilizes the movement of the piston within the bore and provides the means for using the movement of the piston to perform work. As the fluid pressure within the bore is varied, the piston moves reciprocally within the cylinder and its motion is transferred, via the bracket, through the slot to the trolley.
Sealing of the slot and the stability of the piston during its reciprocal movement frequently create difficulties which result in inefficiencies in the rodless power cylinder. A variety of solutions have been proposed to maintain an adequate seal of the slot and the stability of the piston during movement.
The slot in the cylinder in prior art rodless cylinders is frequently sealed through an arrangement utilizing two seals. These seals lock either to each other or to the cylinder, one seal being disposed outside the bore and the other seal being disposed within the bore. One configuration where the seals lock to the cylinder is disclosed in U.S. Pat. No. 4,991,494 to Migliori, where a pair of reinforced strips are utilized to seal the outside and the inside of the slot. The strips include ridges which sealingly engage offset grooves formed in the cylinder. The offset placement of the these grooves does not effectively utilize the minimal amount of available space in the upper portion of the cylinder.
It is also important that the trolley assembly stabilizes the piston during its reciprocal movement. While most prior art devices utilize a single linear bearing disposed between each side of the cylinder and the trolley, in many applications this is insufficient to maintain the desired degree of stability. Thus, there remains a need for a rodless power cylinder which includes means for successively sealing the slot during the reciprocal movement of the bracket while effectively utilizing the space of the upper portion of the cylinder and enhancing the stability of the piston during its movement.